I wouldn't worry too much about levelling dps, although I understand it can be frustrating. The trouble with playing a kitty is that levelling dungeons require a lot of target switching and the mobs die very fast - and we're not well equipped for either of these things. As a rule, the longer a mob lives, the higher our damage will be!

-Sibylle

"Not a shred of evidence exists in favor of the idea that life is serious." (Brendan Gill)

It looks like you are high enough level to have Savage Roar and the Glyph of Savagery. Use that glyph and make sure to cast Savage Roar before you charge in to attack a mob. That will add 30% to all your attacks. Also, even when questing, use a Rake first before you start your Mangles. You also have Faerie Fire available, which is really useful for pulling mobs when questing and also applies an armor debuff to the mobs that will increase your damage. When you are in a dungeon it is useful to keep the armor debuff up all the time. Are you using any of the feral-specific addons? It is hard to say which of them will work for a low-level feral, but you might try Badkitty and/or Droodfocus to help you track the armor debuff from Faerie Fire, Rake, Rip and Savage Roar.